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The requierements for a patent are
novelty
inventive step
(called non obviousness in the US)
usability.
Novelty is anchored in 35 USC 102, which reads
(a) NOVELTY; PRIOR ART.—A person shall be entitled to a patent unless—
(1) the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available ...
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